The present invention relates to a distance measuring device for collating image data of an object (target) such as a vehicle or person on the basis of the spatial frequency characteristics, and measuring the distance to the target from the collation result, and a three-dimensional image measuring apparatus for measuring the three-dimensional image of the target from the collation result.
As a conventional distance measuring device of this type, the following device is available. In this device, a target is picked up by two cameras. A window is set on a target image portion of one image. To check whether any portion of the other image coincides with the image in the window, the images are shifted from each other pixel by pixel to search for a position where the sum total of the absolute values of the differences between the respective pixels become minimum. The distance between the images at this position is detected as the shift between the images picked up by the two cameras. The distance to the target is then measured on the basis of this shift.
As a conventional three-dimensional image measuring apparatus of this type, an apparatus whose main part is shown in FIG. 42 is available. Referring to FIG. 42, reference numeral 1 denotes an image receiving section having a CCD camera 1-1 and a light source 1-2; and 2, a rail. In this three-dimensional image measuring apparatus, the image receiving section 1 moves along the rail 2 to scan a still object (the cross-sectional shape of a human face in this case). More specifically, the image receiving section 1 is moved while light from the light source 1-2 is irradiated on the human face. With this operation, the silhouettes of the human face like those shown in FIGS. 43A, 43B, and 43C are respectively obtained at time T.sub.1, time T.sub.2, and time T.sub.3. By receiving such images piece by piece, the cross-sectional shape of the human face, i.e., the three-dimensional image of the object, is measured.
In such a conventional distance measuring device, however, it takes time to obtain an image shift. In addition, since a window must be set, complicated processing is required. Furthermore, the use of the two cameras leads to a high cost.
In such a conventional three-dimensional image measuring apparatus, it takes time to perform measurement. In addition, since a moving mechanism is required to move the image receiving section 1, the cost of the apparatus is high. Furthermore, objects to be measured are limited to still objects. When, therefore, the cross-sectional shape of the face of a person is to be measured, he/she must be kept still.